A conventional optical sensor has a configuration with a small-sized die stacked on a large-sized die, wherein the large-sized die is electrically connected to the substrate by wire-bonding at a periphery portion of the large-sized die. However, during the wire-bonding of the conventional optical sensor, since the periphery portion of the large-sized die is suspended over the substrate, an external force exerted by the wire-bonding can often result in defects within the conventional optical sensor.